Taiwan Semiconductor Corporation KBU404G

Overview

KBU404G from Taiwan Semiconductor is a 4A, 400V repetitive peak reverse voltage (V_RRM) glass-passivated standard bridge rectifier in KBU package, featuring 150A surge capability, 1.1V max forward voltage at 4A, and <5µA reverse current at 25°C - deployed in AC/DC front-end stages of compact switching mode power supplies.

For engineers reviewing the KBU404G datasheet, KBU404G pinout, KBU404G application, or KBU404G equivalent, key selection criteria include V_RRM = 400V, I_F = 4A, thermal resistance R_θJC = 4°C/W, and UL recognition E-326243 - critical for adapter and lighting power supply reliability validation.

Technical Context

The KBU404G integrates four silicon diodes in a single-phase full-wave bridge configuration with glass-passivated junctions for enhanced moisture and contamination resistance. Its KBU molded package supports PCB mounting with matte tin-plated leads compliant to J-STD-002 solderability and JESD201 Class 1A whisker resistance.

Thermally, it delivers R_θJA = 19°C/W (free-air) and R_θJC = 4°C/W, enabling operation up to T_J = 150°C. Electrical behavior is characterized by low leakage (≤5 µA @ 25°C), high surge tolerance (I_FSM = 150A, 8.3ms), and junction capacitance of 240 pF per diode at 1 MHz / 4V.

Key Specifications

Pinout & Package

Package: KBU - molded plastic case with 4 axial leads (AC1, AC2, +, −), UL 94V-0 rated, 7.2g weight, 0.56 N·m max mounting torque.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar bridge rectifier applications.

Compared with GBU4K and W04, the KBU404G offers balanced trade-offs: UL recognition and lower R_θJC (4°C/W) enable superior heatsink-coupled thermal management, while its standardized KBU footprint simplifies sourcing and manufacturing across multiple OEM platforms.

Availability

KBU404G is available at Aetrix Electronics and suitable for switching mode power supplies, AC/DC adapters, and LED driver power supplies requiring stable component supply, consistent parametric performance, and UL-recognized reliability.

Supply support for KBU404G includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Taiwan Semiconductor Corporation (TSC) is a vertically integrated analog and discrete semiconductor manufacturer headquartered in Hsinchu, Taiwan, serving global power, automotive, and industrial markets since 1979.

The KBU404G belongs to TSC's standard bridge rectifier product line, engineered for cost-effective, high-reliability AC/DC conversion in consumer and industrial power supplies where safety certification, surge resilience, and thermal stability are primary design requirements.

FAQ

What is the maximum repetitive peak reverse voltage (V_RRM) for the KBU404G?

The KBU404G has a V_RRM rating of 400 V, as confirmed in the Absolute Maximum Ratings table of the official Taiwan Semiconductor datasheet (Version J2103). This value defines the highest reverse voltage each internal diode can block repeatedly without breakdown, making it suitable for 230V_AC mains applications with adequate safety margin.

Does the KBU404G require a heatsink in typical 4A continuous operation?

The KBU404G can operate at 4A continuous current without an external heatsink only if ambient temperature remains ≤45°C and PCB copper area meets minimum thermal pad recommendations. With R_θJC = 4°C/W and R_θJA = 19°C/W, derating begins above 70°C ambient - a heatsink is recommended for sustained 4A loads in enclosed or high-temperature environments.

Is the KBU404G RoHS compliant and lead-free?

Yes, the KBU404G is RoHS compliant and features lead-free matte tin-plated leads, verified per Taiwan Semiconductor's documentation (Version J2103). It satisfies J-STD-002 solderability requirements and passes JESD201 Class 1A whisker testing, ensuring compatibility with modern Pb-free reflow processes.

What is the marking code printed on the KBU404G body?

The KBU404G is marked "KBU404G" on its case, followed by date code (YWW format) and factory code (F), as shown in the Marking Diagram section of the Taiwan Semiconductor datasheet. This marking confirms the exact voltage grade (400V) and distinguishes it from other family members like KBU403G (200V) or KBU405G (600V).

Can the KBU404G replace the KBU406G in a 800V design?

No, the KBU404G cannot replace the KBU406G in an 800V design. The KBU404G is rated for V_RRM = 400V, while the KBU406G is rated for 800V. Substituting the KBU404G would risk catastrophic reverse breakdown under normal operating voltage - always match V_RRM to the circuit's peak reverse stress requirement.